EXHIBIT 23

            Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in the Registration Statements
(Forms S-8 No. 333-98801 and No. 333-66741) pertaining to the Penwest
Pharmaceuticals Co. 1997 Equity Incentive Plan, in the Registration Statement
(Form S-8 No. 333-66747) pertaining to the Penwest Pharmaceuticals Co. 1997
Employee Stock Purchase Plan, in the Registration Statement (Form S-8 No.
333-66739) pertaining to the Penwest Pharmaceuticals Co. Savings Plan, in the
Registration Statement (Form S-8 No. 333-66733) pertaining to the Penwest
Pharmaceuticals Co. 1998 Spinoff Option Plan, in the Registration Statements
(Form S-3 No. 333-32940, No. 333-65840 and Amendment No. 1 thereto, Form S-3 No.
333-108513 and Form S-3 No. 333-121332) of Penwest Pharmaceuticals Co. and in
the related Prospectuses of our reports dated March 10, 2005, with respect to
the consolidated financial statements and schedule of Penwest Pharmaceuticals
Co, Penwest Pharmaceuticals Co.'s management's assessment of the effectiveness
of internal control over financial reporting, and the effectiveness of internal
control over financial reporting of Penwest Pharmaceuticals Co, included in this
Annual Report (Form 10-K) for the year ended December 31, 2004.

                                                           /s/ Ernst & Young LLP
Stamford, Connecticut
March 14, 2005